Residual Atrazine Research Articles

Degradation of Atrazine by an Anaerobic Microbial Consortium Enriched from Soil of an Herbicide-Manufacturing Plant.

Atrazine is an important herbicide that has been widely used for weed control in recent decades. However, with the extensive use of atrazine, its residue seriously pollutes the environment. Therefore, the microbial degradation and detoxification of atrazine have received extensive attention. To date, the aerobic degradation pathway of atrazine has been well studied; however, little is known about its anaerobic degradation in the environment. In this study, an anaerobic microbial consortium capable of efficiently degrading atrazine was enriched from soil collected from an herbicide-manufacturing plant. Six metabolites including hydroxyatrazine, deethylatrazine, N-isopropylammelide, deisopropylatrazine, cyanuric acid, and the novel metabolite 4-ethylamino-6-isopropylamino-1,3,5-triazine (EIPAT) were identified, and two putative anaerobic degradation pathways of atrazine were proposed: a hydrolytic dechlorination pathway is similar to that seen in aerobic degradation, and a novel pathway initiated by reductive dechlorination. During enrichment, Denitratisoma, Thiobacillus, Rhodocyclaceae_unclassified, Azospirillum, and Anaerolinea abundances significantly increased, dominating the enriched consortium, indicating that they may be involved in atrazine degradation. These findings provide valuable evidence for elucidating the anaerobic catabolism of atrazine and facilitating anaerobic remediation of residual atrazine pollution.

Differential interference of copper with endophytic bacterial inoculation: Atrazine decontamination in Acorus tatarinowii and culture solution

To clarify the interference effects of inorganic ions, Acorus tatarinowii and endophytic bacterium Herbaspirillum huttiense (Hh) were combined to decontaminate atrazine pollution under different copper levels. This study verified inoculation effects and revealed the complicated processes of atrazine transformation in solutions. 35.9% leaf biomass was promoted by Hh inoculation, and the value was lowered to 7.87% by high doses of copper. The changing trend of leaf N, K, and S contents, and tiller numbers were consistent with that of leaf biomass. Hh injection improved atrazine accumulation by 43.5% in roots, and under copper interference, this value lowered to 10.6%. Hh promoted atrazine deethylation in plants, which was copper-dose dependent in different plant organs. In solutions, atrazine was conjugated with small-molecule secretions at m/z 118, detoxicated into 2-hxydroatrazine and 2-hydroxy-4-acetamido-atrazine, then the triazine ring opened. Copper interference had a more significant impact on residual atrazine conversion products than Hh inoculation treatments. Hh treatment promoted the ring-opening degradation of atrazine in water. The addition of high doses of copper ions promoted the oxidative process of atrazine while inhibiting its ring-opening transformation process in water.

Atrazine pollution in groundwater and raw bovine milk: Water quality, bioaccumulation and human risk assessment

Atrazine herbicide can bioaccumulate over time and thus affect humans for generations to come. However, scarce studies have evaluated its bioaccumulation potential in bovine milk, a nutritional staple for children and the elderly both domestically and internationally. This study aimed to determine its concentration in groundwater and bovine milk, as well as the risks it is likely to pose for human health. Eighteen dairy farms in the Pampean plain of Argentina were analyzed. A strong correlation was found between the chemical composition and the geomorphological characteristics of the plain. In addition, increased salinity was observed in the groundwater at greater distances from the aquifer's recharge area. Atrazine was quantified in 50 % of the groundwater samples (at values ranging from 0.07 to 1.40 μg/L), and in 89 % of the bovine milk samples (from 2.51 to 20.97 μg/L). Moreover, atrazine levels in 44.4 % of the groundwater samples and 11.1 % of the bovine milk samples (n = 18) exceeded the limits internationally established as safe for human consumption. The hazard quotient (HQ) values of the compound were negligible for children and adults, both in groundwater (child = 9.7E-4, adult = 4.5E-4) and in milk (child = 1.0E-2, adult = 1.6E-3). The estimated cancer risk (CR) values need further evaluation (child = 7.8E-6, adult = 3.6E-6 in groundwater; child = 6.6E-5, adult = 1.3E-5 in milk). In both types of samples, the HQ and CR of residual atrazine were higher for children than for adults. Nevertheless, bioaccumulation factors suggest that dairy cows have a moderate capacity to incorporate atrazine from abiotic matrices. This is the first report on residual atrazine in bovine milk in Argentina. The results presented here indicate that the status of atrazine contamination in the area should continue to be monitored in order to assess its long-term impact on public health.

Degradation of Residual Herbicide Atrazine in Agri-Food and Washing Water.

Atrazine, an herbicide used to control grassy and broadleaf weed, has become an essential part of agricultural crop protection tools. It is widely sprayed on corn, sorghum and sugar cane, with the attendant problems of its residues in agri-food and washing water. If ingested into humans, this residual atrazine can cause reproductive harm, developmental toxicity and carcinogenicity. It is therefore important to find clean and economical degradation processes for atrazine. In recent years, many physical, chemical and biological methods have been proposed to remove atrazine from the aquatic environment. This review introduces the research works of atrazine degradation in aqueous solutions by method classification. These methods are then compared by their advantages, disadvantages, and different degradation pathways of atrazine. Moreover, the existing toxicological experimental data for atrazine and its metabolites are summarized. Finally, the review concludes with directions for future research and major challenges to be addressed.

Integration of Metabolomics and Transcriptomics for Investigating the Tolerance of Foxtail Millet (Setaria italica) to Atrazine Stress

Foxtail millet (Setaria italica) is a monotypic species widely planted in China. However, residual atrazine, a commonly used maize herbicide, in soil, is a major abiotic stress to millet. Here, we investigated atrazine tolerance in millet based on the field experiments, then obtained an atrazine-resistant variety (Gongai2, GA2) and an atrazine-sensitive variety (Longgu31, LG31). To examine the effects of atrazine on genes and metabolites in millet plants, we compared the transcriptomic and metabolomic profiles between GA2 and LG31 seedling leaves. The results showed that 2,208 differentially expressed genes (DEGs; 501 upregulated, 1,707 downregulated) and 192 differentially expressed metabolites (DEMs; 82 upregulated, 110 downregulate) were identified in atrazine-treated GA2, while in atrazine-treated LG31, 1,773 DEGs (761 upregulated, 1,012 downregulated) and 215 DEMs (95 upregulated, 120 downregulated) were identified. The bioinformatics analysis of DEGs and DEMs showed that many biosynthetic metabolism pathways were significantly enriched in GA2 and LG31, such as glutathione metabolism (oxiglutatione, γ-glutamylcysteine; GSTU6, GSTU1, GSTF1), amino acid biosynthesis (L-cysteine, N-acetyl-L-glutamic acid; ArgB, GS, hisC, POX1), and phenylpropanoid biosynthesis [trans-5-o-(4-coumaroyl)shikimate; HST, C3′H]. Meanwhile, the co-expression analysis indicated that GA2 plants had enhanced atrazine tolerance owing to improved glutathione metabolism and proline biosynthesis, and the enrichment of scopoletin may help LG31 plants resist atrazine stress. Herein, we screened an atrazine-resistant millet variety and generated valuable information that may deepen our understanding of the complex molecular mechanism underlying the response to atrazine stress in millet.

Biochar alleviated the toxicity of atrazine to soybeans, as revealed by soil microbial community and the assembly process

Atrazine has a detrimental effect on soybean growth in corn-soybean rotation systems. A knowledge gap exists regarding how rhizosphere microbial interactions respond to atrazine stress, and specifically, whether they may alleviate the detriment of atrazine on soybeans, this serving as a target to alleviate the adverse impact. Biochar are widely used for remediation in herbicide contamination soil, however, little is known about how biochar fuels the microbiomes in rhizosphere to improve soybean performance. We investigated the response of the microbial community to atrazine stress with and without biochar application to soybean cultivation in a greenhouse experiment. Atrazine had detrimental effects on soybeans and nodules, reshaping the microbial community in both the bulk and rhizosphere soil. Biochar application was able to ameliorate atrazine effects on soybean and nodule activity, with an increase in competition among microbes in the soybean rhizosphere soils. Biochar favored the probiotics such as the bacteria Lysobacter, Paenarthrobacter, and Sediminibacterium in the rhizosphere soils. The relative abundance of Lysobacter exhibited strong-negative correlations with potential pathogens. Elastic net regression with bioindicators and environmental factors accurately predicted the residual content of atrazine in soil. Collectively, our results provide a practical strategy of using biochar to improve soil quality for corn-soybean rotation that is contaminated with residual atrazine. Overall, beneficial plant microbes and changes in microbial interactions and assembly processes in the soybean rhizosphere are capable of alleviating atrazine stress on soybean growth.

Use of Eichhornia crassipes and Pistia stratiotes for environmental services: Decontamination of aquatic environments with atrazine residues

There is a need for efficient technologies to remove atrazine residues that are detected in water bodies. These residues are harmful as they intoxicate plankton and may decrease oxygen in the water. This study evaluated the growth, physiology, and leaf anatomy of Eichhornia crassipes and Pistia stratiotes that were exposed to atrazine for phytoremediation purposes. To carry out this evaluation, atrazine concentrations ranging from 0 to 1000 μg L-1 were added into 5 L pots with macrophytes, which were maintained for 28 d in these solutions. Following this period, atrazine toxicity, chlorophyll content, and dry mass were measured. High-performance liquid chromatography was used to quantify residual atrazine concentrations in the solution and plant material samples. It was found that E. crassipes was sensitive to an atrazine concentration of 1000 μg L-1. Atrazine reduced macrophyte growth, promoted a decrease in chlorophyll, and altered anatomical parameters; however, plant growth was uninterrupted, and macrophytes remained physiologically active until the evaluation period. The residual atrazine concentrations in solution were 35.56% and 79.19% for E. crassipes and 76.13% and 78.83% for P. stratiotes, respectively; this was lower than plants that were unpotted for atrazine concentrations of 10 and 100 μg L-1. The results indicate that E. crassipes and P. stratiotes may be suitable phytoremediators in aquatic ecosystems for atrazine concentrations up to 10 and 100 μg L-1, respectively.

Modeling Bioavailability Limitations of Atrazine Degradation in Soils

Pesticide persistence in soils is a widespread environmental concern in agro-ecosystems. One particularly persistent pesticide is atrazine, which continues to be found in soils and groundwater in the EU despite having been banned since 2004. A range of physical and biological barriers, such as sorption and mass-transfer into bacterial cells, might limit atrazine degradation in soils. These effects have been observed in experiments and models working with simplified systems. We build on that work by developing a biogeochemical model of the degradation process. We extended existing engineered system models by including refined representations of mass-transfer processes across the cell membrane as well as thermodynamic growth constraints. We estimated model parameters by calibration with data on atrazine degradation, metabolite (hydroxyatrazine) formation, biomass, and isotope fractionation from a set of controlled retentostat/chemostat experiments. We then produced site-specific model predictions for arable topsoil and compared them with field observations of residual atrazine concentrations. We found that the model overestimated long-term atrazine biodegradation in soils, indicating that this process is likely not limited by bioavailability or energetic constraints of microbial growth. However, sorption-limited bioavailability, could explain the long-term fate and persistence of the main degradation metabolite hydroxyatrazine. Future studies should seek alternative controls that drive the observed atrazine persistence in soil. This work helps to bridge the gap between engineered and natural systems, allowing us to use laboratory setups to gain insight into real environmental systems.

Effects of Atrazine on Chernozem Microbial Communities Evaluated by Traditional Detection and Modern Sequencing Technology.

Atrazine is a long residual herbicide commonly used in maize fields. Although atrazine can effectively control weeds and improve crop yield, long-term application leads to continuous pollution in the agricultural ecological environment, especially in the soil ecosystem, and its impact on soil microorganisms is still not clear. Four methods were used in the experiment to clarify the effect of atrazine on the bacterial populations of cultivated soil layers of chernozem in a cold region in different periods: high-performance liquid chromatography (HPLC), colorimetry, microplate, and high-throughput sequencing. The level of residual atrazine in cold chernozem decreased from 4.645 to 0.077 mg/kg soil over time, and the residue gradually leached into deep soil and then decreased after accumulating to a maximum value. Atrazine significantly affected the activities of urease and polyphenol oxidase activity in the soil layers at different periods but had no significant effect on sucrase and phosphatase activity. Atrazine significantly reduced the diversity of microbial carbon source utilization and total activity in soil layers of 0–10 and 20–30 cm but only reduced the diversity of microbial carbon source utilization in the 10–20 cm layer. Atrazine had no significant effect on bacterial populations (10–12 phyla, 29–34 genera), but had a slight effect on the relative abundance of various groups. Atrazine significantly reduced the diversity of bacterial populations in cultivated soil layers of chernozem in a cold region, and the diversity of bacterial populations decreased with decreased residue. This lays a foundation for guiding the safe use of herbicides on farmland in Northeast China.

Upward translocation of acetochlor and atrazine in wheat plants depends on their distribution in roots

Residual acetochlor and atrazine in soils, resulting from their extensive application to maize plants, may affect product safety of the ultimate wheat crop. To determine the potential uptake and accumulation of acetochlor and atrazine by wheat plants, the uptake mechanism, translocation, and subcellular distribution of these two herbicides were studied through hydroponic experiments (10 mg L−1). The results indicated that acetochlor can be taken up through the apoplastic pathway and can accumulate in wheat roots with little upward translocation. However, atrazine could be taken up by roots through the symplastic pathway and subsequently transported to the stems and leaves. Little upward translocation of acetochlor in wheat plants was due to its preferential distribution into root organelles with higher lipid contents. Conversely, the low bioconcentration of atrazine in root organelles and cell walls after uptake led to its easy upward translocation. Uptake of acetochlor and atrazine by wheat roots and the distribution of atrazine to the stems and leaves were predicted well by using the partition-limited model. The obtained results indicated that residual atrazine in soil may be taken up by wheat roots and acropetally translocated, thereby posing a threat to product safety of wheat.

Separation and detection of trace atrazine from seawater using dummy-template molecularly imprinted solid-phase extraction followed by high-performance liquid chromatography.

A novel sample pretreatment strategy for separation and detection of atrazine from seawater was established with molecular imprinting solid-phase extraction (MISPE). Cyromazine was used as dummy-template based on computational analysis to synthesize dummy-template molecularly imprinted polymers (DMIPs) as sorbent of MISPE for atrazine analysis. The DMIPs were irregular loose porous layered structure characterized by scanning electron microscopy and showed higher binding capacity than non-imprinted polymers through adsorption experiments. An offline MISPE procedure using DMIPs as sorbent coupled with high-performance liquid chromatograph was developed for separation and purification of atrazine from seawater samples. The recoveries of atrazine in the spiked seawater samples ranged from 86.7% to 98.6%, and the relative standard deviation was less than 4.07% (n = 3) under optimal conditions indicating that the proposed method was suitable for the detection of trace residual atrazine in seawater. In addition, no atrazine was detected in three seawater samples from Jiaozhou bay, China.

Short term changes in the abundance of nitrifying microorganisms in a soil-plant system simultaneously exposed to copper nanoparticles and atrazine

Copper nanoparticles (NCu) may co-exist with other pollutants in agricultural soils, such as pesticides. However, this has been little evaluated yet. Thus, possible effects of the simultaneous applications of pesticides and NCu on biogeochemical cycles are expected, for example on the nitrogen cycle. Therefore, the aim of this work was to evaluate the effect of simultaneous application of the herbicide atrazine (ATZ) and NCu on the abundance of total bacteria and nitrifying communities: ammonia-oxidizing archaea (AOA) and ammonia-oxidizing bacteria (AOB). Moreover, the ATZ dissipation was evaluated. A soil-plant system containing ATZ at field dose (3 mg a.i. kg−1) was mixed with two doses of NCu (0.05% or 0.15% w/w). Changes in the abundance of 16S rRNA and ammonia monooxygenase (amoA) genes of AOA and AOB were evaluated by real-time quantitative PCR (qPCR) at three sampling times (1, 15 and 30 days). The residual ATZ and nitrate production were also measured. The results showed significant differences in microbial composition and abundance over the 30 days of the experiment. Particularly, an initial decrease was observed in total bacterial abundance due to the presence of ATZ and NCu respect to ATZ alone (~60%). The abundance of AOA was also remarkably reduced (~85%), but these communities gradually recovered towards the end of the experiment. Conversely, AOB abundance initially increased (>100%) and remained mainly unaltered in soil exposed to ATZ and NCu 0.15% w/w, where nitrate formation was also constant. Moreover, NCu decreased the ATZ dissipation, which was translated in a 2-fold increase on the ATZ half-life values (T1/2). This study demonstrates that the simultaneous presence of NCu and ATZ may represent a risk for the total bacteria present in soil and sensitive microorganisms such as nitrifying communities, and changes in the dissipation of the pesticide could influence this process.

Development of a novel bio-organic fertilizer for the removal of atrazine in soil

The accumulation of atrazine in farmland is prone to cause phytotoxicity to kinds of sensitive crops, such as soybean. In addition, some kinds of agricultural solid wastes have long been considered as the important non-point pollution source. The aim of this experiment was to investigate the feasibility of removing atrazine from soil and alleviating the stress of atrazine on the growth of soybean by application a novel bio-organic fertilizer developed by agricultural solid wastes, such as cow manure organic fertilizer, biochar and poly-(γ-glutamic acid), as well as an atrazine-degrading strain Arthrobacter sp. DNS10. Sixteen potential bio-organic fertilizer formulations were designed by D-optimal mixture design of Design Expert software and atrazine-removal ability was selected to single out the optimal formulation. As a result, the optimal formulation of bio-organic fertilizer (named as DNBF10) was produced by the cow manure organic fertilizer 76.20%, biochar 4.46%, poly-(γ-glutamic acid) 8.63% (m/m) and the number of Arthrobacter sp. DNS10 with 0.91 × 108 CFU/g. The atrazine removal percentage of DNBF10 for the atrazine in soil with the initial atrazine concentration 15.26 ± 0.49 mg/kg was 95.05% after 10 days' application with DNBF10 at the adding dosage of 5 mg/kg (relative to the dry weight of the soil). Furthermore, pot experiment results suggest that the growth of soybean seedlings in the soil (initial atrazine was 8.14 ± 0.16 mg/kg) that adding both of DNBF10 (25%) and chemical fertilizer (75%) were better than those of the treatment only adding chemical fertilizer (100%) under the same nutrient addition level. All the results indicate that the application of DNBF10 was a new alternative to reuse the typical agricultural solid wastes, as well as to reduce the harm caused by residual atrazine to soybean.

Changes in atrazine speciation and the degradation pathway in red soil during the vermiremediation process

Atrazine (2-chloro-4-ethylamino-6-isopropylamino-1,3,5-triazine) is a triazine herbicide intensively used in agricultural production and is often detected in different environmental matrices at concentrations above the permitted limit. This study investigated the influence of two earthworm species (epigeic Eisenia foetida and endogeic Amynthas robustus) on atrazine speciation and the degradation pathway. Our results revealed that both earthworms significantly accelerated atrazine degradation in a 28-day vermiremediation, and the residual atrazine declined from 4.23 ± 0.21 mg/kg in bulk soils to 0.51 ± 0.29 mg/kg (E. foetida) and 0.43 ± 0.19 mg/kg (A. robustus). By consuming organic matter (from 40.37 ± 1.14 to 36.31 ± 1.55 and 34.59 ± 1.13 g/kg for E. foetida and A. robustus) and neutralizing the soil pH (from 5.37 ± 0.27 to 6.36 ± 0.11 and 6.61 ± 0.30 for E. foetida and A. robustus), both earthworms reduced humus-fixed atrazine and increased the available atrazine. The percentage of available atrazine increased from 8.80 ± 0.21% in bulk soil to 10.30 ± 0.29% and 16.42 ± 0.18% in the vermiremediation treatments. Both earthworms promoted the hydroxyatrazine pathway by consuming soil organic matter and encouraged the deethylatrazine/deisopropylatrazine pathway by neutralizing the soil pH. Our findings unravel a new mechanism of vermiremediation by improving the soil physical-chemical properties and altering the atrazine degradation pathway, providing new insights into the influential factors on atrazine bioremediation in red soil.

Sorption, kinetics and thermodynamics studies of atrazine herbicide removal from water using iron nano-composite material

Atrazine organic pollutant has been found in several water resources of the world. It is highly toxic and carcinogenic in nature. Atrazine is removed by adsorption on iron composite nanoparticles. The composite nanoparticles were synthesized, analyzed and applied for atrazine uptake from water. Residual atrazine was monitored by gas chromatography–mass spectrometry. The maximum atrazine removal (95 %) was achieved using contact time 30.0 min, concentration 30.0 µg/L, pH 7.0, dose 2.5 g/L and temperature 20.0 °C. The adsorbent was selective for atrazine adsorption. The results obeyed Langmuir, Freundlich, Temkin and Dubinin–Radushkevich isotherms. ΔG° values were −6.05, −6.11 and −6.15 kJ/mol at 20, 25 and 30 °C temperatures, respectively. The value of ΔS° was −2.45 × 10−3 kJ/mol K. It showed decline in entropy of atrazine uptake. The adsorption followed pseudo-second-order kinetics. The adsorption mechanism was liquid film diffusion. The proposed adsorption method is inexpensive, fast and reproducible. It can be used to remove atrazine from any water sample/source.

Biodegradation of atrazine by Arthrobacter sp. C3, isolated from the herbicide-contaminated corn field

The s-triazine herbicide, atrazine, has been well acknowledged as an important source causing contamination of soil, water, and sediment. Functional bacteria are one of the critical candidates for removing residual atrazine from contaminated environments. Here, seven bacterial strains showing atrazine-degrading ability were isolated from long-term atrazine-contaminated corn field and identified based on 16S rRNA gene sequencing. Among these bacterial isolates, a bacterium, later designated as Arthrobacter sp. C3, was found to be capable of completely degrading 25 mg/l atrazine. The high-performance liquid chromatography-mass spectrometry (HPLC-MS) analysis indicated that the atrazine was dechlorinated to hydroxyatrazine, a non-phytotoxic compound. The functional gene, trzN, which participates in the first step of atrazine degradation was successfully amplified and showed high similarity to the known trzN genes from different bacterial genera. Based on the HPLC-MS and the functional gene analysis, the functional bacterium C3 was speculated to degrade atrazine via dechlorination, which detoxified the herbicide. This study suggested a great potential of Arthrobacter sp. C3 to be used in indigenous bioremediation of atrazine in field.

Bioremediation strategies for removal of residual atrazine in the boreal groundwater zone

Strategies for bioremediation of atrazine, a pesticide commonly polluting groundwater in low concentrations, were studied in two boreal nonagricultural soils. Atrazine was not mineralized in soil without bioremediation treatments. In biostimulation treatment with molasses, up to 52% of atrazine was mineralized at 10 °C, even though the degradation gene copy numbers did not increase. Incubations with radioactively labeled atrazine followed by microautoradiographic analysis revealed that bioremediation strategies increased the relative proportion of active degraders from 0.3 up to 1.9% of the total bacterial count. These results indicate that atrazine degradation might not solely be facilitated by atzA/trzN-atzB genes. In combined biostimulation treatment using citrate or molasses and augmentation with Pseudomonas citronellolis ADP or Arthrobacter aurescens strain TC1, up to 76% of atrazine was mineralized at 30 °C, and the atrazine degradation gene numbers increased up to 10(7) copies g(-1) soil. Clone libraries from passive samplers in groundwater monitoring wells revealed the presence of phylogenetic groups formerly shown to include atrazine degraders, and the presence of atrazine degradation genes atzA and atzB. These results show that the mineralization of low concentrations of atrazine in the groundwater zone at low temperatures is possible by bioremediation treatments.

Field Dissipation of Atrazine and Metribuzin in Organic Soils in Florida

Sugarcane growers have observed reduced residual activity of atrazine on organic soils in the Everglades Agricultural Area (EAA) of south Florida. Field studies were conducted between 2011 and 2012 to determine the rate of dissipation of atrazine at 2.24, 4.48, and 8.96 kg ha−1and metribuzin at 0.56, 1.12, and 2.24 kg ha−1in the top 10 cm of soil in sugarcane fields in the EAA. The bioavailable fraction of atrazine dissipated more rapidly than the total amount of atrazine in the soil. Half-lives of the total and bioavailable fraction of atrazine ranged between 3.9 to 12.1 d and 1.0 to 7.5 d, respectively. Metribuzin dissipated much more slowly than atrazine on organic soils. Similarly, dissipation of the bioavailable fraction of metribuzin was more rapid than was the dissipation of the total amount of metribuzin in the soil. Half-lives of the total and bioavailable fraction of metribuzin ranged between 16.2 and 24.8 d and 6.0 and 14.3 d, respectively. These results indicate that enhanced atrazine degradation occurs on organic soils under field conditions in the EAA, resulting in shorter residual atrazine activity. This implies that metribuzin is a better option for weed control in sugarcane grown on organic soils of the EAA exhibiting enhanced atrazine degradation.

Chemical Modification and Degradation of Atrazine in Medicago sativa through Multiple Pathways

Atrazine is a member of the triazine herbicide family intensively used to control weeds for crop production. In this study, atrazine residues and its degraded products in alfalfa (Medicago sativa) were characterized using UPLC-TOF-MS/MS. Most of atrazine absorbed in plants was found as chemically modified derivatives like deisopropylated atrazine (DIA), dehydrogenated atrazine (DHA), or methylated atrazine (MEA), and some atrazine derivatives were conjugated through different functional groups such as sugar, glutathione, and amino acids. Interestingly, the specific conjugates DHA+hGSH (homoglutathione) and MEA-HCl+hGSH in alfalfa were detected. These results suggest that atrazine in alfalfa can be degraded through different pathways. The increased activities of glycosyltransferase and glutathione S-transferase were determined to support the atrazine degradation models. The outcome of the work uncovered the detailed mechanism for the residual atrazine accumulation and degradation in alfalfa and will help to evaluate whether the crop is suitable to be cultivated in the atrazine-polluted soil.

The combined effects of atrazine and lead (Pb): Relative microbial activities and herbicide dissipation

The experiment was conducted to investigate the effects of single and combined pollution from different concentrations of atrazine (field rate, FR, 2.0mgkg−1 and 5 times FR, 10mgkg−1) and lead (Pb) (300mgkg−1 and 600mgkg−1) on enzyme activity, basal soil respiration (BSR), and net nitrogen (N) mineralization (NNM) in soil after exposure for 0, 7, 14, 21, and 28 days. In addition, residual atrazine was measured in the samples of combined contamination. Results showed that the notable effects of either or both contaminants on the microbial activity and biological processes. Enzyme activity data demonstrated that the order of sensitivity to contamination was urease>invertase>catalase. BSR was strongly stimulated by atrazine/Pb at the early exposure (0–7 days for single contaminant and 7–14 days for combined contaminants). The stimulation effects on BSR were higher at low concentrations of the contamination (FR and Pb300). The combined treatments of 5FR+Pb600 inhibit BSR and NNM. Overall, the parameters associated with N cycling (urease and NNM) were more sensitive than others. Both Pb concentrations (300 and 600mg/kg) had little influence on the dissipation of high concentrations of atrazine (5FR) during the 28-day-incubation. This study has provided useful information on potential ecotoxicology effects of combined contamination of atrazine and Pb on relative microbial biological process.